Double-blind studies are commonly conducted to determine the efficacy of a new drug therapy. In double-blinded studies neither the physician nor the patient know if the active agent or its placebo had been administered. This is done to insure objectivity when evaluating study end-points. With oral and intravenous medications it is relatively simple to prepare active agent (vehicle and agent) and the appropriate placebo control (containing vehicle only, without active agent). When studying site specific therapies, which is typically accomplished using an infusion catheter, there is concern regarding the active delivery of placebo to the site.